1. Field of the Invention
The present invention relates to a fractionating apparatus having a probe for dripping a sample liquid fed from a liquid feed mechanism such as an HPLC (High Performance Liquid Chromatograph), or the sample liquid with an additive agent, as a liquid droplet from a tip portion of the probe onto a plate such as a microplate or sample plate, and preparing a sample to be analyzed with MALDI-TOF-MS (Matrix Assisted Laser Desorption Ionization Time-Of-Flight Mass Spectrometry) or FT-IR (Fourier Transform Infrared Spectrophotometer).
2. Description of the Related Art
In the related art, when a sample liquid such as eluate from the liquid chromatograph is fractionated and captured on a sample plate for an analyzer of MALDI-TOF-MS or the like, for example, the sample liquid is automatically dripped and fractionated from the probe onto the sample plate. Usually, the fractionating apparatus has an X-Y stage and a Z stage, in which the sample liquid is fractionated and captured by moving the sample plate in the horizontal and vertical directions. In dripping the sample liquid, the sample plate is raised to approach a lower end face of the probe, and the sample liquid emerging from the lower end face of the probe is contacted with and moved onto the sample plate.
Such probe of the fractionating apparatus is made of stainless, fused silica, or PEEK (polyether ether ketone).
However, since stainless, fused silica or PEEK used as the material of the probe has poor hydrophobic property, when a liquid having great surface tension such as water is flowed, a liquid droplet may rise up the outside surface of the probe, depending on the surface tension of the sample liquid to be dripped. As a result, if a sample liquid amount reaches a uniform amount essentially fractionated on the sample plate, and the sample plate is raised to approach the lower end face of the probe, the liquid droplet does not make contact with the sample plate and is not fractionated, so that the amount of fractionation is varied at each spot.
In order to solve the above-mentioned problems, it is common practice that the material of the probe is fused silica capillary, and Teflon (registered trademark) is coated to increase the hydrophobic property on the surface of the capillary. However, a special coating technique is needed to coat Teflon on the surface of the probe, and the surface of the probe coated with Teflon does not withstand the service for a long time due to a life of coating.